


Section 1

by thebicyclefandom



Series: 123 Robotics Experiments for the Evil Genius [1]
Category: The Avengers (2012)
Genre: Engineering, Gen, Physics, Robots
Language: English
Status: Completed
Published: 2013-01-05
Updated: 2013-01-14
Packaged: 2017-11-23 18:02:33
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 5
Words: 6,263
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/625045
Author URL: https://archiveofourown.org/users/thebicyclefandom/pseuds/thebicyclefandom
Summary: <blockquote class="userstuff">
              <p>Tony gets asked to write a children's how-to book on robotics. When he gets banned from his lab, he actually gives it a try.</p>
            </blockquote>





	1. Introduction To Robotics

**Author's Note:**

> I got a book for Christmas titled "123 Robotics Experiments For The Evil Genius."
> 
> ...it was very dryly written. I thought of Tony. This happened. Time to learn about engineering, everyone!

"Director Fury, with all due respect - "  
  
"Stark, you don't have the _capacity_ to give that much respect."  
  
"...ok, possibly true, noted, with all the respect I can possibly muster for anyone - "  
  
"Just spit it out."  
  
"This is a terrible idea. This is a really horrible, terrible idea."   
  
The look Fury gave Tony took unamused to a new level. Even Coulson couldn't look that unamused, and Tony had a private suspicion that Coulson practiced his varied unfazed looks in a mirror every night. Tony was beginning to understand why Fury had gotten the role of Director.   
  
"While I certainly agree that they're overestimating you, the NSF are insisting, and I find it's usually a good idea to stay on their good side. They do fund most of our R&D projects, you know."  
  
"Hey, I have offered to build and invent all SHIELD's gear. I make that offer every two weeks or something. Look, this is me offering again, I'll build all of SHIELD's gear, I'll even do it for free, you don't even need to beg."  
  
"You'd build an override into every system and hide it in overly complicated schematics. The technicians wouldn't have a hope in hell."  
  
"....I might not."  
  
"The fact that you push the issue every "two weeks or something" says that you would. And that's beside the point. If you don't write this book, I will revoke every waiver of every assessment you have ever skipped. You'd better bring a sleeping bag with you to Psychiatric, because you won't be leaving for a while."  
  
Tony knew that he shouldn't have skipped so many assessments. Really, he should have known better than to give Fury any leverage over him.   
  
One last shot.  
  
"Do you really think it's a good idea for me to write a book on engineering to give to kids? Just consider for a moment everything that's come out of my workshop, ever. I think the least deadly thing in there is my phone, and my phone shoots lasers."   
  
"On the contrary, I understand that you have several worker bots."  
  
"I - how do you even know that? You aren't allowed in my workshop, I do not allow SHIELD agents in my workshop, I don't even let Coulson into my workshop, and he can't have hacked in, I upgraded the security after the last time he broke into my apartment. Besides, my bots shoot lasers too."   
  
"Get to it, Stark, and get out of my office. If you have that much trouble, start by making robots out of cardboard and pipe cleaners or something."  
  
Yeah, right. Easy. Just write a book on how to make robots, Tony thought resentfully. Like that's not a recipe for disaster.


	2. Toilet Paper Roll Mandroid

It was two weeks before Fury sent Steve to nag Tony.  
  
Well, that wasn't strictly accurate. There was no nagging involved and Fury didn't actually send Steve after him specifically. Overall it was a pretty inaccurate statement, although Tony would stick with it regardless. Everyone else would say that it was two weeks before anyone had a chance to pressure Tony into starting the damn book.  
  
In Tony's defence, he'd gotten himself beaten to a pulp in the latest battle against Hammerdroids. The injuries weren't the problem. Hammer had one-upped him, through something as basic as an EMP no less. The result was Tony retreating into his workshop and throwing, in essence, a temper tantrum. He spent a week and a half locked in with JARVIS and a blowtorch before Pepper put her foot down. At two o'clock in the morning she triggered the emergency override, putting JARVIS into lockdown and cutting off all electricity - including both the backup generators - to the both the workshop and R&D.  
  
She then proceeded to break in half an hour later - Tony hadn't even known that workshop door _had_ a manual key - and drag him to the kitchen. Tony didn't realise just how badly he'd overexerted himself this time until he had to climb the stairs leaning on Pepper's shoulder and the handrail in equal quantities. He cursed her for cutting off power to the elevators, then stopped and cursed her for interfering all the damn time.  
  
"Tony, you need to take a break," she informed him firmly, once she got him seated and plied him with leftovers (who even cooked?) and coffee.  
  
"No I don't, I'm fine. Look: food, caffeine, I'll even sleep for an hour if you really insist but I'm absolutely fine -"  
  
Gesturing was a bad idea. Pepper could see the burn marks on his hands when he gestured. Bad idea.  
  
"-except for a few minor injuries, but it's fine, really." Tony sighed as Pepper reached for his hand, tentatively turning it over to examine the shiny new skin, the half-healed scratches. When she looked back up at him, there was something else threaded through the scowl. Something a lot like fear.  
  
"Tony, I haven't seen you this bad since the last time you invented while drunk."  
  
Tony winced a little at that. He'd nearly lost his arm when trying to use a piece of steel as a chalkboard. The slab in question was in the process of being laser-cut. Rhodey had removed all the hidden stashes of alcohol from his Malibu workshop that night while a hysterical Pepper took him to the hospital. That had been eight weeks before Afghanistan.  
  
For the first time since the Hammerdroid attack, Tony actually checked the state of his hands.  
  
They were a wreck of half-healed wounds and calluses, pink burns and infected cuts. He started becoming aware of how painful they were; even bending his fingers sent jolts down his fingers.  
  
Ok, so maybe Pepper had a point. And he should probably make a note to never engineer while angry. It was a little alarming how long the list of restrictions was getting.  
  
"Fine. Fine, they're not pretty. What do you expect me to do though, stop working, because you know what happened the last time you tried that -"  
  
"I expect you to get some sleep," Pepper told him with a scowl and Tony was getting a little irritated with people cutting him off. Both his speech and his actions, come to think of it. Then again, he was sleep-deprived to the point of delirium, so interruption was the only way to shut him up. "You can find something else to do in the morning," Pepper added, a little more gently. She was making puppy eyes. He hated it when she made puppy eyes. He also hated it when she was right. He could never argue with her when she combined the two.  
  
Tony started to stand with a sigh, trying to ignore the way the room spun. As he pulled his scarred hand from Pepper's grip, she said hastily, "You're not sleeping in the workshop." He smiled in resignation, altering course for the bedroom he seldom occupied.  
  
*  
  
It was a little weird to be up at seven am. Who was awake at seven am? No one sensible, Tony concluded as he walked out to the kitchen.  
  
He was wrong. Steve was sitting at the table in sweaty gym clothes, laughing with Natasha and Coulson. Bruce leant against the counter sipping tea with a smile on his face, and Tony was suddenly forced to face the fact that two-thirds of the Avengers kept normal hours.  
  
For some reason, that was a little upsetting.  
  
Bruce was the first to spot him lurking in the doorway, and waved him in. The others registered his presence immediately, but he noticed none of them seemed particularly surprised to see him up.  
  
"We were just about to have breakfast, if you want to join us," Steve offered, pointing at a spare chair. Tony accepted the seat, wondering why he hadn't heard of this early morning gathering.  
  
"I'm fine, I ate last night," he replied with a shrug, and Natasha stifled a snigger as Steve rolled his eyes.  
  
"You know, normal people eat three meals a day, Tony," Steve said in a mock earnest voice.  
  
"Citation please. I don't know where you sourced that information, but it's not from this household," said Tony. "But if you really insist." He glanced around at everyone before adding, "You don't seem all that surprised to see me."  
  
Steve shrugged, but it was Coulson who answered."Ms Potts called."  
  
"This morning?" Tony asked. How could so much have happened before seven in the morning?  
  
"Last night," Coulson clarified, and Tony realised that maybe no one kept normal hours in the Tower after all.  
  
"Uh huh. And you guys have been told to keep me out of trouble?"  
  
There was a pause that Tony felt was somewhat ominous as Steve, Natasha and Coulson exchanged looks, and he could swear he heard Bruce's low chuckle behind him.  
  
"We decided to help you kill two birds with one stone," Steve began, pausing in confusion as Coulson and Natasha both winced nearly imperceptibly.  
  
"You're going to start writing that book for Fury," Natasha said brusquely, taking over from Steve.  
  
Tony didn't even try to stifle his groan. "Really?"  
  
"Yes." Her tone brooked no argument, and Tony slumped down in his seat a little.  
  
"I don't even know where to start," he admitted. He looked beseechingly at Banner. "Bruce, buddy, help me out. Tell them how hard it is to explain science to people who don't science."  
  
Bruce didn't look up as he responded, "You want me to explain to them why you can't do what an average high school teacher does everyday?"  
  
"Y-no, that's not - high school teachers don't even count as scientists, that's -"  
  
"Why aren't robots humanoids?" Steve asked mildly and Tony fell silent for a second.  
  
"That's ridiculous, bipedal robots would require extremely complicated programming just to walk which makes them nigh useless and it's hard enough just to get them to stand upright - "  
  
But Tony could see what Steve was getting at, so he slowed down and stopped to think about it for a moment, ignoring the incredulous looks of the SHIELD agents at the table and Steve's smirk.  
  
"Ok, let's try something," Tony murmured at length. "I'll need some cardboard and pipe cleaners. And some adhesive."

**Notes for the Chapter:**

> Wait there's...plot? Where did that even come from?
> 
> So this is (one of) my first fics (I have been writing for, like, three weeks? Not even that.) and this whole fandom thing is a really alien world like whoa so comments, concrit, hell, even outright insults, are welcome. Feel free to shoot me an ask over at http://thebicyclefandom.tumblr.com!


	3. Pipe Cleaner Insect

**Notes for the Chapter:**

> This fic is probably going to oscillate between ridiculous, educational and dramatic. Just a heads up. This chapter is long and engineery, but I later on intend to (maybe) illustrate most of the content through events, not exposition.
> 
> But this is SCIENCE and also FICTION and sometimes exposition, y'know, happens. 
> 
> If you see any weird formatting/things framed with stars *like this* please let me know!

It didn't start _terribly_. Clint enthusiastically joined the hunt for resources as soon as he woke up; Thor accompanied Steve to the craft shop and delighted over every product he passed. Meanwhile, Tony made rough sketches of his proposed "experiments" - very rough sketches, as his aching hands had stiffened overnight. Natasha quizzed him as he worked, and based on her questions he had come up with four "models" to illustrate his points.  
  
They ran into trouble before they even began when Coulson found ten rolls worth of toilet paper on the floor of the bathroom. After he amicably threatened to call Pepper and hide all of Clint's bows - including the one hidden above the workshop - Clint and Tony spent an hour sitting on the bathroom floor wrapping the toilet paper back onto the rolls.  
  
Clint grumbled about Coulson knowing way too much, but Tony was very interested to hear that Clint had a nest in the airducts leading to his workshop. It certainly explained a few things.  
  
Steve made another trip to the craft shop, sans Thor.  
  
It was nearly eleven by the time they were ready to go, and Tony was feeling even more ridiculous, but Natasha had her camera ready and the supplies were neatly arranged and everyone was looking at him expectantly.  
  
Tony figured he might as well just get on with it.  
  
"Alright. Robots. Captain Oldschool here wanted to know why my drones don't all look like C3P0." Tony was relieved that no one looked confused at the reference. Progress! "In the 50s - a little after Steve's time, I suppose - scientists - human scientists, at least - decided that the best form was humanoid because humans are arrogant like that. But standing on two feet also means we can actually do things with our hands, so someone decided that if we ever met aliens, they'd be bipedal because you can't build things without free hands. Trust me. I've tried.  
  
"Now I think about it, they were right," he mused, glancing at Thor. "Anyway, most sci-fi writers apply the same logic to robots."  
  
Steve and Thor were both nodding, which made Tony feel a little better, but Clint was creating a bow out of the pipe cleaners, so he figured he should move this on a bit.  
  
"The easiest way to show you why this is a stupid notion - no offence, Steve - is to create a bipedal thing - that's not organic, since robots, well, aren't - and see how well it moves. Toilet paper rolls stand up by themselves, right? So we're going to make one of these." Tony tapped the first of his sketches lightly. It showed a "model" with a central torso in two pieces, and two arms and two legs, complete with "knees" and "elbows".  
  
"Note that the pipe cleaners attach on particular sides to simulate joint movement. I'm not sure what pipe cleaners will stick to so everyone's got a different type of adhesive."  
  
Tony was a genius. Really, he was. But no matter how which way he looked at it, he could not work out how a highly trained team of warriors could be so easily defeated by kindergarten-level arts and crafts.  
  
Clint insisted on using the model plane cement, then went into a sulk when it failed and made glasses out of the pipe cleaners instead. After discovering that contact cements were similarly terrible, Natasha started to make a scale model of a Glock 13mm pistol with cut-up toilet rolls. She could strip it down and put it back together, and Tony was more scared of her than ever.  
  
Thor used epoxies to no effect, and joined Clint making stick figures and battling them. Tony was seriously wondering how anyone in the room got through Psych before he remembered why he was doing this in the first place. Evidently, Fury signed off on more Psych waivers than his.  
  
Coulson and Bruce didn't take part in the activity but instead kept a dry running commentary on the war between Thor and Clint's stick people.  
  
To nobody's surprise, Steve got it right. Not only did he get the PVA, which actually stuck to the pipe cleaners, he also had the steady hands and patience required to make the toilet paper roll mandroid.  
  
Tony was using the Krazy Glue, but apparently the methods used in metalworking were not the same as those required for crafts. He pulled a face as he tried to pull sticky pipe cleaners off his hand, and somehow brushed the scraps of cardboard from Natasha's gun. Coulson broke off his commentary on the pipe cleaner for long enough to point it out.  
  
"Stark, one day you'll have to tell us all how you conned everyone into believing you are an engineer."  
  
Tony's face flushed and his expression turned ugly as Clint looked up in delight, sensing a chance to pick a fight. Tony took a breath and ran a hand through his hair, regretting it immediately when several pipe cleaners lodged themselves in his hair. He ignore Clint's shout of laughter and pasted an indifferent look on his face.  
  
"Hey, I skipped grade four or whenever it was that people learn to do this," he said, gesturing expansively at the trashed tabletop, pipe cleaners falling off his hands as he did. "Or was it grade five? Because I skipped that too, you know." He tried to surreptitiously brush some of the cardboard off his hands and didn't react as the flash of Natasha's camera went off. He would find a way to get that photo deleted later.  
  
"Besides, at least one of us achieved the objective," he continued, grabbing Steve's model.  
  
"And it wasn't you," Steve reminded him, taking the mandroid back. "What am I supposed to be doing with this thing?"  
  
Tony shrugged. "Get it to stand up."  
  
Steve tried. He really did. Tony actually felt bad for him, and even after the model was passed around the table and came back, Steve was still trying.  
  
It wouldn't stand, of course, and Steve knew it. It simply collapsed into a tangled puddle of toilet paper rolls.  
  
"Not a particularly auspicious start to robot-making, Stark," Clint remarked, watching Steve in sympathy.  
  
"That's the point," Tony explained. "Bipedal robots _sound_ really cool, but even getting them to stand upright is an overly complicated process. Why do you think we don't have robot butlers yet? Most androids don't move and half of them don't even have legs because why would you bother with all that hassle? It takes humans years to work out how walking works, and we're a lot smarter than robots. Well, some of us are, at least. JARVIS is smarter than 80% of America, but then, it is America."   
  
"I don't understand how you can be so unpatriotic," Steve said, frowning. "Besides, why did we bother with this whole thing if you knew the outcome?"  
  
"You really have to see it to understand," Tony explained. "Like, when I was young, even though I knew that theoretically it just didn't work well, I didn't actually learn my lesson until I tried to build a bipedal friend when I was ten, and it did....pretty much what you just saw except heavier and more painful because it fell on top of me."  
  
There was a stunned pause. "You tried to build a friend?" Clint finally asked, an odd note in his voice. Tony suspected it was laughter, but it was hard to tell. He cringed inwardly at his mistake in word choice.  
  
"Not a...friend exactly, it was just a robot. A lackey. C'mon, every ten-year-old wants to built a robot. Most just don't have the resources to do it," he corrected. Everyone continued to stare at him, and he was beginning to change his mind about the laughter. Laughter he could deal with. This silence felt a lot like pity.  
  
"Is JARVIS a lackey?" Natasha asked. As usual, Tony couldn't read her voice, but he was getting a little unnerved.  
  
"Ok, I thought I was doing this to get _out_ of Psych evals, so can we quit the nobody-loved-me routine and get on with robots?" he asked a little more sharply than intended. He cleared his throat and tapped his second blueprint harder than intended, gritting his teeth as pain rang through his fingers.  
  
"Obviously bipedal robots are out of the question here," he started. "Now if there's one thing we engineers love to do, it's plagiarize nature's designs. Mother Nature, unlike, I don't know, Justin Hammer and most other human engineers barring myself, is a good engineer whose complex designs actually, you know, work.  
  
"There aren't all that many bipedal creatures in nature, which probably should have told us something, so the obvious next step is quadrupedal animals, but I'll skip the experiment and you'll just have to take my word that it's too complicated to worry about for the most part. They can stand up, but getting them to walk takes forever and always comes with irreconcilable issues anyway. Mobility is only one component of a robot, so you don't really want to spend forever trying to get it to work."  
  
Tony glanced up from the table and was relieved to see that everyone had stopped giving him weird looks. In fact, the majority of them looked at least vaguely interested.  
  
He continued in relief, "Quadrupedals can at least stand upright, though, which is, y'know, a start, so obviously more legs is better here. So our next option is six. Considering the sheer number of bugs in the world - and there is a lot, don't visit the Amazon because you'll meet most of them and there's no decent bars - but anyway, considering the number of bug species, six legs is at least worth a shot."  
  
The next thing Tony got them to do - since Tony appointed himself supervisor and subsequently excused himself from craft work - was make an egg-carton ant. To prevent another fiasco, they only made the one, and Steve did all the gluing. They took turns fiddling with the legs as Tony explained. It felt an awful lot like Show and Tell.  
  
"Obviously we could just make millipede bots and stop worrying about the number of legs, but the more complicated something is the worse it breaks down, so this is it. If you want a robot with legs, insectoid is the way to go. It ticks both movement boxes: stays upright, can move. Even if it stalls midstep or something, an insectoid bot won't fall over. the weight's centered, too, which is where you want it."  
  
Tony paused to make sure everyone seemed sufficiently involved enough.  
  
"So. We've got the bug-thing standing, so let's talk about movement. There's six legs, which is three on each side, so at any one time an insectoid can balance on three legs - the center leg of one side, and the outer two of the other side." Steve lifted the three legs up, and miraculously, the egg-carton thing stayed up.  
  
"So, three legs move at any one time, going up, forward, down." Steve mimicked the movements on the bug. "Yeah, just like that. And then the other three legs do the same thing.  
  
"So to move this thing, we have four movements we need: up, down, forward and back. Which, really, is two movements, or rather, two degrees of freedom -"  
  
"Lost," Clint called, putting a hand up. Thor followed suit, and Tony sighed, pulling the bug blueprint towards him.  
  
"You get the bit about needing four movements, right?" he asked as he gingerly picked up a pencil. Clint shrugged, shaking his head and Tony fought the urge to roll his eyes. "Ok. Up," he instructed Steve, trying very hard not to sound condescending. Tony wasn't sure when he became so invested in making the other Avengers understand his craft. "Forward. Down. And see how the non-active legs automatically bend back? So that's four motions." Clint nodded slowly, and Tony drew on the blueprint a two-part leg with two hinge joints: a horizontal shoulder hinge and a vertical "knee" hinge.  
  
"This is how you'd do it. Doing this the other way would be awkward and inefficient, although I guess it would still work. So this," and he drew a sweeping curve from left to right on the shoulder hinge, "is your first degree of freedom. That's what we call this arc thing. This," he indicated the up-down arc of the knee, "is the second. Your human shoulder has three. The maximum you can have in a single limb is six, although you usually don't need that many."  
  
Clint nodded again, and even Natasha was watching. Tony felt oddly pleased that they were all following.  
  
"What if the legs couldn't support the body?" a voice queried softly, and Tony looked up with a start. He hadn't even realised Bruce was listening.  
  
"Well, that's the first flaw with insectoids," Tony admitted, fighting his pride at the fact that Bruce was actually thinking about this, about the limitations. Then again, Bruce was actually a scientist, so thinking about limitations was part of his job, but it was a start. "The second is that this is still pretty complicated, considering all we want it to do is get from A to -"  
  
Everyone's phone started ringing at once and the Tower siren started blaring, and Tony was actually pretty disappointed, considering he didn't want to do this thing in the first place. The Avengers leapt to their feet, Tony included, before he remembered that his suit was lying dismantled in his locked workshop. As Tony faltered, Thor clapped a sympathetic hand on his shoulder that made him stagger.  
  
If anyone thought that Tony cleaning up was out of character they didn't let it on, and he was grateful because he needed something useful to do with his hands, in spite of their soreness. If there was anything Tony hated, it was being useless.  
  
Besides, he needed to clear the space for the next lesson.  
  
He also needed Lego, he thought as he set Natasha's gun on the microwave and pulled the last shards of cardboard and dried glue off his hands.

**Notes for the Chapter:**

> If you have any questions about the physics/technicalities/ROBOTS, feel free to ask me! I'm hardly an expert, but one of my specialties is cutting through wordiness/sciencey vocab and putting things a little more plainly. But seriously, I promise that in Section 2 I'll try to make the science less dialogue and more event. 
> 
> Shoot me an ask at http://www.thebicyclefandom.tumblr.com if that's how you roll! Thanks for reading.


	4. LEGO Mobile Robots

While the battle wasn't particularly fierce, Clint spent the night in Medical (again) and Thor was called back to Asgard for ambiguous "family business" (again).  
  
Tony had tried to get into his lab while the Avengers were out. He'd found a sign on the door. In Pepper's neat hand were the words, "I've changed the access codes and set an alarm. Don't even try it." He took that as an official ban.  
  
After calling her and arguing and whining and pleading, he eventually he gave up. Another half hour of boredom later, he begrudgingly accepted the suggestion and began writing the first chapters of the book.   
  
Of course, by 'write', he meant 'dictate' because Tony Stark rarely writes anything. That's what PAs and CEOs and handlers and JARVIS are for.   
  
Bruce found him lying on the couch sometime after midnight, muttering into a Bluetooth earpiece and playing with LEGO wheels.   
  
"I take it your enforced 'break' doesn't include proper sleep schedules," Bruce remarked when Tony finally drew breath. Tony gave a violent start and fell off the couch gracelessly. Bruce politely refrained from laughing, but Tony still glared at him as he picked himself up.   
  
He murmured "pause dictation" under his breath, before haughtily replying, "I slept last night, thank you very much."   
  
Bruce did laugh at that. "Tony, one day we're going to put you in a room and educate you on normal living habits."  
  
"You're awake too," Tony pointed out with a pout. Bruce's smile fell, and Tony regretted mentioning it.   
  
"Guilt," Bruce admitted sheepishly. "Hawkeye's in Medical because of me."  
  
Tony scoffed. "Hawkeye spends every second mission in Medical, it's really not a big deal. He didn't even get concussion this time, I wouldn't worry about it if I were you." Bruce shrugged, but Tony knew he wasn't going to drop the issue, so he patted the couch next to him, shifting his legs to make room. "Come play LEGO with me."  
  
Bruce's smile returned, and Tony wondered for a moment how the man kept his cheerful mask so well. "I'm struggling clicking the pieces together," he confessed, flipping his hands over to reveal the healing yellow bruises and the blisters that have started crusting over. His fingertips were still a mess. While he knew he *could* fight through the pain, he knew better than to do so for something like LEGO.   
  
Bruce accepted the colourful blocks curiously. "What do you want me to do with them?"  
  
"Ok, see this platform? Click it on top of this thing here - the spine - yeah, like that. Axels here and here. OK, attached the spine to this pivot - that's it, that's all I wanted for that one." Bruce looked at the completed but crude wagon with faint amusement, and Tony shrugged self-consciously.   
  
"More robotic motion?" Bruce asked with a grin, and Tony ducked his head.   
  
"I didn't really think it was a good idea to let Barton loose with LEGO," Tony said and Bruce's smirk widened again. "I have two more, if you're having fun."

**Notes for the Chapter:**

> Since this is a short chapter, I'll provide you with some quotes from the book this is based on, 123 Robotics Experiments For The Evil Genius.
> 
> Myke's Rules of Robotics:  
> "3. Jerkiness in a robot is not a selling point."  
> "6. The faster a robot runs, the more impressive it is."  
> "8. Complexity adds weight."  
> "9. Weight adds weight."
> 
> Introduction to Robotics:  
> "Just remember that if you create a robot to take over the world and it fails, wen the authorities come, you've never heard of me or this book."
> 
> Toilet Paper Roll Mandroid:  
> "To cut pipe cleaners, I used a set of wire clippers - don't use scissors (especially ones that are important to other people.) I shouldn't have to say this, but you should wait for toilet paper rolls to become available; don't expedite the process of getting bare toilet paper rolls. I don't want to get any angry emails from parents saying that one day they walked into their bathroom and found enough toilet paper lying on the floor to fill 10 rolls."
> 
> "You may want to try using a cyanoacrylate such as Krazy Glue to hold down the pipe cleaner pieces before using the paper or wood glue. Personally, I would discourage doing this as you will probably end up gluing yourself to short pieces of pipe cleaner and empty toilet rolls. After other people see this, it will be hard for them to think of you as an "Evil Genius" with any kind of seriousness."
> 
>  
> 
> I'll probably include further quotes in the end notes of each relevant chapter from now on.


	5. Cardboard Arm

**Notes for the Chapter:**

> This is your warning that this is a science chapter. A conversational science chapter involving LEGO and army drill words, but science nonetheless! 
> 
> For those who don't know, I have corrected chapter three: the maximum degrees of freedom for a single limb is only six - three translation, three rotational - and the shoulder joint has three (although the entire arm has seven: shoulder/three, elbow/one, wrist/two, hand/one (opening and closing)).

To Tony's utter surprise, it was Thor who suggested the next robotics lesson. 

Thor was the last person Tony would have guessed to bring it up. Tony actually had a list in his head ranking each Avenger most likely to ask to least, and Thor was the very last person on it. Tony would have guessed someone put him up to it, except he seemed to understand the concepts of the last lesson, and had brought back sketches of six-legged Asgardian beasts to show Tony. 

"I struggle to understand many aspects of Midgard," he stated, when Tony pressed him. "It is more heavily mechanized than my own world. Your instruction helps me to understand the limits of your technology." He paused thoughtfully for a moment before adding, "Perhaps that is why there are fewer scholars in Asgard. We no longer seek advancement, thus no one learns the trades necessary to advance us." 

Tony made a mental note to teach Thor some basic physics some day soon, but in the meantime, he had two more basic units to cover in Introduction. Not that he'd admit to planning chapters or lessons. 

He made sure to have everyone gathered by eight. Now that he'd started getting up before lunchtime, he'd noticed that villains were apparently not morning people, which explained why Steve had not, to date, turned up to a mission briefing in gym gear. 

He briefly toyed with the idea of keeping this relatively normal work schedule once his workshop restriction had been lifted, but dismissed it immediately. Old habits and all that.

The kitchen was once again full, and on the desk, Tony had the first makeshift wagon. 

"Where's my LEGO?" Clint asked before Tony could get started.

"I didn't have enough to hand out," he snapped, but Clint wasn't deterred that quickly.

"Why not?"

"Too expensive," Tony replied dryly. Clint snorted in laughter. "If you want the truth, I was trying to slow your regression into childhood. Maybe you should get that checked." 

"I would if I could, but the shrinks hate me for some reason," Clint smirked.

"If you teach me your secret, I'll buy you LEGO," Tony offered, and it was fun to see Coulson's shoulders slump. It made a nice contrast to Clint's reaction.

"If you make it the Avengers mega set, I'll also tell you how to get released early from Medical every time." That explained a lot.

"Looking to play with yourself, Clint?" Natasha asked dryly.

"I do that everyday anyway." He answered without missing a beat.

"LEGO for secrets, done. You better pay attention though, and no talking in my class," Tony warned. "We were talking about creepy-crawly bots last week, right? I'm sure you've noticed there's none in my workshop. Partly because they're called creepies for a reason, and partly because it's impractical.

"So the other obvious option for a moving robot base is wheels. Pretty simple, right? Except wheeled platforms are more complicated to turn than they really have any right to be."

Tony gestured at the LEGO wagon. "Who wants to test-drive it?" 

Clint immediately put his hand up, but Tony chose Thor, since Thor had shown so much interest before. It had nothing to do with Clint being an idiot. Nothing at all.

Thor ran it forward and back, turning it and increasing speed when Tony asked. After it had tipped for the second time, he began to explain, using a second cart. His cart consisted of little more than four wheels on a slab.

"See, when a car turns, this inner wheel has to turn more sharply, than the outer - ". He paused, seeing the confusion in Steve and Thor's faces, the small frown lines in Natasha's brow and tried to think of a better way to explain. 

Wheel. There's a word.

"Ok, Cap. You know when you're marching in a squad - which sounds like a really boring way to travel, by the way - and you do a, I don't know, wheel right or turn or whatever?"

"Right wheel," Steve corrected, looking befuddled.

"Yeah, yeah. If you're the inner guy, do you have to take really little steps and turn really tightly?"

"Step short," said Steve absently. "Yeah, and the outer rank steps out."

"Yes. That. It's the same principle. The inner wheel of a car has to spin slower and turn sharper," Tony said, and understanding lit up Steve's face and Tony was relieved. One down. Everyone else to go.

Except it's not everyone else. The other's faces were clearing, the imagery of marching soldiers illustrating the concept better than Tony anticipated. 

"Ok," Tony began hesitantly, "so the issue with this one," he pointed to the wagon without a pivotal bearing,"is that there's no way to change the angle or speed on each wheel. There are things called linkages, which are built into cars, and you can build them into a robot but it includes messy unnecessary things like angles.

"This one," he continued, picking up the first wagon, "has a central steering wheel." He held the top platform and flicked one of the wheels, and all four spun on the central shaft. "It's not perfect, but it works. There's another way to get around the angle thing, though. Anyone got any ideas?"

His heart sank as the faces around the table looked back blankly, and he mentally cursed himself for thinking this would work, but Coulson put his hand up.

Tony just raised his eyebrows, and Coulson's hand was back down before he suggested, "Three wheels."

Tony couldn't stop the grin splitting his face. It was very difficult to not hug the man right there, although the knowledge that Coulson was armed certainly helped.

"Yes! Yes, you make a tricycle. Which is the technical term for that bot base and I'm not even being facetious about that."

Tony picked the remaining two LEGO constructions up from the floor, noting with satisfaction that his fingers didn't hurt at all any more. He was almost sad that he'd be giving up these lessons in a couple of days.

Almost, but not quite. He missed the smell of tarnished metal and his suit took priority over brats learning robotics.

Clint's hand was up before Tony had even put the constructions on the table. 

"If you pull it apart before I'm done, you will never get new arrows from me again," Tony warned, wondering once again when this had come to matter so much. 

Clint rolled the two-wheeled platform around on the table with gusto as Tony finished his spiel. "The other way to fix the whole spinning-wheels thing is to separate the two wheels. It's called a differentially driven robot base. Which sounds really nasty but is basically a tank or a bulldozer base. Well, with wheels instead of tracks but it's the same principle. Tank bases are called tracked differentially driven bases, since tracks and differentially driven robot bases. Look simple terms, it's two wheels or tracks that move independently of each other."

"That's not really simple terms, Stark," Natasha said, straight-faced, but Steve waved her comment aside.

"We've got it, Tony," he said reassuringly. In reward, Tony rolled the final wagon to Steve. It was similar to Clint's, but with four wheels again. Instead of each wheel being linked to its opposite, it was linked to its neighbour. 

"Reduces turning resistance," Tony shrugged in explanation when Steve gave him an enquiring look.

Tony let them play with the carts while he texted Pepper a request to order the Avengers mega set of LEGO. Clint had miraculously left his LEGO car intact and was playing bumper-cars with Bruce, who had acquired the better of Thor's two wagons. Natasha and Coulson were consorting in whispers over Steve's bot and Tony had to wonder why *he* had the reputation for weaponizing everything.

After five minutes, when the novelty had worn off, Tony pulled his final prop out from under the table. 

He had no idea how to call them to attention - this wasn't a school, for god's sake - but Bruce put his cart down and looked expectantly at Tony, and the others followed suit.

"Er. Right, one final area. Obviously, robots don't just exist to drive around in circles - except Roombas, I guess - so the other thing to think about is their appendages. What are you, twelve?" he asked in disgust as Clint snickered at the word. "Their arms." 

Tony passed the arm - two tubes of cardboard joined by more pipe-cleaner - to Natasha. Clint's eyes shone, but Tony cut him off before he'd fully drawn breath.  
"Steve made it, ok? Look, it shares some similar characteristics - is that the right word? - to the leg; there's the degrees of freedom and the joints. The end thing is called an end effector. It obviously doesn't have to be a gripper, although it often is. 

"The way a lot of robotic arms are programmed is through recorded movement. Someone just stands there and moves the arm, and it records it and plays it back. That's, like, construction machinery stuff. Obviously mine are more complicated - they're more like the space robot arms, which have to use algorithms because recorded movement doesn't work so well in zero gravity."

"You use space robots in your workshop?" Steve asked, bemused.

"Yes, I do. The actual formula for calculating the position of the end of a robotic arm is pretty simple - basic trigonometry. Preschool stuff."

"Trigonometry is high school curriculum, Tony," Bruce noted mildly. Tony made a dismissing gesture with his hand. 

"The range of motion is known as a work envelope. That's pretty much it," he concluded lamely. "Er, questions, queries, doubtful points?"

"Are you including these props in the book?" Coulson asked.

"I wasn't planning to, but...". The more Tony thought about it, the better the idea seemed. After all, the constructions had kept the Avengers occupied; he imagined the average eleven-year-old would appreciate them too. "Maybe. Anyone else?"

"When's the LEGO gonna get here?" Clint asked. Now he had taken the carts apart. All of them. Natasha and Coulson had moved over and were sharing their ideas as he attempted to build a mega-wagon that carried Natasha's gun.

Perhaps using the Avengers as testers was innacurate. The average eleven-year-old was more mature than several of the Avengers combined.

**Notes for the Chapter:**

> Thus ends Section One: Introduction To Robots! Once again if you find anything you don't get or that sounds wrong PLEASE let me know! That applies to both my writing and the science. 
> 
> Section Two: Robot Structures will hopefully start next later this week.
> 
> Thanks for reading! Corrections, comments, compliments, criticism and insults are all welcome.


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